The invention is based on a method for knock detection in an internal combustion engine according to the species defined by claim 1.
It is known that internal combustion engines with a knock control use knock sensors, which transmit output signals that permit detection of whether or not a knocking combustion is occurring. For example, body noise sensors are used for knock detection, wherein there are embodiments with a single knock sensor, with two knock sensors which are attached to predeterminable locations on the engine block, or with a knock sensor for each cylinder. The problem in evaluating the signals from the knock sensors lies in that the signal produced by the knocking must be separated from the signals produced by other noise. Since both the knock signal and the background signal depend on various operating conditions of the internal combustion engine, carrying out the knock evaluation as a function of the speed of the engine is already known.
In a device for knock detection known from DE-P 43 32 711, there is a description as to how the output signals of two knock sensors are processed for knock detection. In a microprocessor, prior knock signals are used to generate reference levels, which are compared to the current output signal which corresponds to a prepared knock sensor signal. If the signal exceeds the reference level, then knocking is detected and a corresponding control, e.g. of the ignition, is carried out, which assures that no further knocking occurs in the subsequent combustions. In order for the speed dependency of the background signal and the knock signal is taken into consideration and an optimal knock detection can be executed, the reference level is changed as a function of the speed, wherein as the speed increases, the reference level is increased as well.
The method for knock detection according to the invention, with the characteristics of claim 1, has the advantage that a reliable knock detection is possible over the entire working range of the engine, independent of the intensity of the noise. This advantage is achieved by virtue of the fact that in addition to the usual reference level tracking, an improved reference level tracking is carried out in the event of dynamics, particularly for internal combustion engines that have a sharp noise increase. Even in engines with above average noise production or in ranges with an above average noise increase, a false detection of knocking does not occur since in this case as well, a reference level adaptation advantageously occurs.
Further advantages of the invention are achieved by means of the steps taken in the dependent claims. In this connection, it is particularly advantageous that the improved reference level tracking in the event of dynamics permits a quicker tracking of the reference level. This rapid tracking is achieved by virtue of the fact that the associated factor in the dynamic case is reduced in comparison to the normal case.